Method of rolling titanium sheets



Y test purposes. been hot rolled into heavy gauge sheet on thesameequipment as used for stainless steel, but

- itself;

Patented Sept. 8, 1953 UNITED STATES PATENT OFFICE 2,651,099 METHOD OFROLLING TITANIUM SHEETS James A. Roemer, Warren, Burt H. McKibben,

1 ,Niles, ;and Joseph R. Corry, Mineral Ridge,'

Ohio, assignors, by mesne'assignments, to Mallory-Sharon TitaniumCorporation, Niles, Ohio,

a corporation of Delaware No Drawing. Application November 17, 1950,Serial No. 196,352

'physical and chemical propertiesparticularly its lightness in Weight,its strength, and its corrosion resistance-are manifold.

Titanium has been used Widely for many years 7 in the form offerro-titanium or ferrocarbontitanium as a deoxidizing material in themanufacture of basic steel, because of its high afiinity for both oxygenand nitrogen. It also has been -.used as an alloying agentin steel andaluminum.

However, little actual experience has been had and little use. has beenmade of pure metallic titanium because of the present high cost ofreducing the metal from ore to metallic form. As i a result, onlyextremely small quantities of pure -metallic titanium have beenprocessed in an experimental manner to form small titanium bars andshort, narrow sheet thickness sections for Some titanium is said to havesuch procedure is laborious and costly and does not provide light gauge,hot rolled titanium sheet material finished in sizes and gaugescomparable to sheet steel for use in pressing, stamping, drawingorotherwise forming large sheet titanium components, parts or devices.

Pure titanium ingotshave only been available in weights ranging from 40to 650 pounds and wound in shape, being produced either by are orinduction melting of sponge titanium. Sponge v titanium is produced byseparating the iron and titanium from ilmenite (iron-titanium ore) toform titanium oxide which is converted to titanium tetrachloride. u Thelatter, when redu'ced with molten magnesium, forms sponge titanium andmagnesium tetrachloride.

The problem of rolling pure titanium into large size, thin gauge hotrolled sheets from such availtitanium when rolled tosheet form,whichprevents it from being satisfactorily doubled, upon An approach-to theproblem is further complicated by the. belief of those Who have Iinvestigated the properties of titanium that the material could notbeheated to a high enough ;;temperature,for obtaining those'reductionsin hot rolling which are. necessary to produce large 12 Claims. (Cl.29-9-19) 1 size, light gauge, titanium sheets without damaging thematerial.'-'

Another factor complicating the problem is the relatively high heatconductivity of pure titanium which results in rapid cooling of theheated material during rolling. This rapid cooling characteristic; inaddition to the relatively low temperatures believed to be required foravoiding damage tothe material, has indicated that great diflicultieswould be encountered in obtaining desired reductions and uniformity ofgauge in attempting to hot roll large size, light gauge, titaniumsheets".

Notwithstanding these difficulties, we approached the problem from thestandpoint of proper controls of rapid heating, rapid and extensivereductions, and surface protection against heat loss and excessiveoxidation, and discovered that puretitanium sheets could be economicallyand satisfactorily rolled in sizes, for example, of 36" x 95" x .020 to36" x 96" x .014", with satisfactory surfaces, free from mill marks, andwith uniform gauge. I

Accordingly,-it is an object of the present invention to provide amethod or procedure of rolling pure titanium into large size, thin gaugesheets of the orderof-36" x 96"- x .020" to 36" x 96" x .014".

Furthermore, it is an object of the present invention to provide amethod or procedure of hot-rolling, pure-titanium to light gauge sheetform with relatively-high rolling temperatures protecting the materialduring'final-stages. of

reduction from rapid loss of heat and from excessive oxidation.

Also, it is an object of the present invention to provide a new methodor procedure by which pure titanium'sheets'may be hot rolledeconomically with existing modern sheet mill equipment.

It is a further object of the present invention to advance the artbyproviding an economical method or procedure for the successfulproduction of large-size, light gauge, ductile, pure titanium sheetswhile avoiding diificulties heretofore believed to be so inherentlyassociated with titanium as to prevent the economicaland satisfactoryDroduction'of such sheets.

- Finally,-it is an object of the-present invention to satisfy theexisting need for large size,

light gauge, ductile, hot rolled, titanium sheets, to solve problemsexisting in the manufacture of the same, to eliminate difficultiesbelieved to be inherent in this field, and to obtain the fore- P goingadvantages and desiderata in a simple. I

economical, and effective manner.

These and other objects andadvantages apparent to those skilled in theart from the following description and claims may be obtained, thestated results achieved, and the described difhculties overcome by thediscoveries, methods, steps, operations and procedures which. comprisethe present invention, the nature of which is set forth in the followinggeneral statement preferred procedural embodiments of which-illustrativeof the best mode in which applicants have contemplated applying theprinciples-are set forth in the following description, and which areparticularly and distinctly pointed out and set forth in the appendedclaims forming part hereof.

The nature of the discoveries and improvements in methods of rollingtitanium sheets may be stated in general terms as preferably includingthe steps of providing pure titanium sheet bar as by forging or rollingthe same from titanium ingots; conditioning the surfaces of the sheetbar; repeatedly heating and elongating the same by single-ply'rolling toheavy gauge sheet form; matching, reheating and rolling such sheets inpairs to further reduce and elongate the same; sandwiching such titaniumsheets between basic steel sheets; and reheating and rolling suchsandwich packs to desired gauge preferably accompanied by doubling.

By way of example, the improved methods and procedures of the presentinvention may be understood by reference to examples hereinafterdescribed in detail. Three round, LO-pound, arcmelted, pure titaniumingots, 5 in diameter and 12 long and containing up to 99.24% tita niumand 36% carbon, after being surface con ditioned in the same manner asother metal ingots to remove scale and surface imperfections by turning,grinding, etc., were heated in a reducing atmosphere in a gas-firedfurnace to approximately 1700" F. to 1800" F. metal temperature,-

and forged on a drop hammer to flatten the same. After the first forgingoperation, the surfaces of the blanks were reconditioned with chippinghammers and grinding wheels in a usual manner, and the blanks werereheated, further hammer forged, again reheated, and finally hammerforged to provide from each ingot one rectangular sheet barapproximately thick by 12" wide by 28" long.

One round, IOU-pound, induction-melted, pure.

titanium ingot,'8" in diameter and 14%;" long, and containing 98.5?titanium, 56% carbon, 22% iron, and 06% nitrogen, was similarly surfaceconditioned to remove scale and surface imperfections, and then heatedin a reducing atmosphere to approximately 1750 F. to 1850 F, metaltemperature, forged on a drop hammer, reheated, and further forged toform a 5 x 5" x 26" slab. This slab was then cut in two to form twoblanks 5" x 5 x 13",and one blank was subjected to three heating andforging steps to form a sheet bar x 12" x 3e", and the second blank wassubjected to two heating and forging operations to reduce the same to asheet bar of similar size.

The five sheet bars thus forged from the 40# and 100# ingots were thensurface conditioned by shot blasting and grinding over all, the endsthereof where not square being machined to provide square ends.

'4 Example: 40 1 One of the 40t ingot sheet bars was heated in acontinuous bar heating furnace under a reduc- :-ing atmosphere to 1520F. metal temperature and given six passes on a 3-high hot mill toelongate the 12"width of the slab to 43", with a finishing speed ofabout 225 feet per minute. The

piece was thenreheated to 1580" F. and given two passes on the 3jhighmill to elongate the same to about b'linches. The piece Was then heatedin a continuous pack heating furnace under a reducing (atmosphere withthe furnace temperature maintained at approximately 1480" F. to

approximately 1350 F. metal temperature and given two single-ply passeson a 2-high hot sheet mill to elongate the piece to 74" long by ,115thick, finishing at a speed of about 225 feet per minute.

The sheet was then sheared in half, matched inapair, and thepair heatedin the continuous pack furnaee to; lii hflf Ffa ndgiven four passes onthe Z-highhot mill to 74" x .059". The pack was then reheated andhot-doubled without roll- .ing and again reheated to 1350? R, and givenfour passes on theJ2-high hot mill, producing four sheets in the packeach .029 thick. The doubled endof the pack containing the four sheetswas shearedaway, andthe four sheets matched with two ordinary or basicsteel sheets of approximately the same size and gauge in a sandwich withthe fourtitaniumsheets in the center and one basic steel sheetabove andanother below the four titanium sheets. This sandwich pack was heatedina continuous pack furnace to 1350 F. and given two passes on the Z-highhot mill to .023" gauge, then hot-doubled, reheated, and given twopasseson the 2-high mill. The eight tita niumand four steel sheets in the packwere then separated, the gauge of the eight titanium sheets thereinbeing from .013" to .014". The finishing temperatureof the titaniumsheets in the pack wasapproximately 1100 F. to 1150" F.

During some of the later rolling steps on the V Z-high hot mill,gasflames were impinged on the rolls in an attempt to keep the rolls ashot as possible to prevent cooling of the titanium sheets duringrolling.

We discovered in carrying out the foregoing procedure in rollingtitaniumto sheets as thin as .013-014" thick, that excellent metalsurfaces resulted on the titanium sheets, with little oxide formedthereon and no mill marks, and the gauge of each sheet was substantiallyuniform throughout. We further discovered in separating the sheets inthe pack that; the titanium sheets did not stick to'the basic steelsheets between which the titanium shects wre sandwiched, and that thetitanium sheets did not stick to each other.

W also discovered that the lower heat conductivity of the steel sheetsbetween which the titanium sheetswere sandwiched held heat in thetitanium sheets longer and enabled more elongation of the titaniumsheets in the pack in one heating than could have otherwise beenobtained. Furthermore, the relatively high rollin temperaturesused'inrolling the titanium sheets enabled the necessary elongation to takeplace required for producing titaniumsheets'as thin as .013- .014"thick.

Also, the sandwiching of the titanium sheets between the basic steelsheets, in the later stages high temperaturesused.

hot mill to an'elongation of ,73

under a reducing atmosphere to la 1580 FL metal" temperature andgivensix passes ona 3;]rii'gh hot mill to an elongation of $91, with a225-feetper-minute finishing speed. The-piece was then taken to acontinuous pack heating furnace where it was, heated, under a recedingarm es-' phere o a m me ely B twesterne ature and given twosingle-ply,passeson a z high c. 9 3 hickee of 122"; finishing t.abqui2 51esL 9rm'mThe sheet was sheared in halL-matched in a pair, and the pair reheatedto l 3 50ffi. in the continuous pack furnace, and then given three s eth .ziehh g i 'tq.6 1122. 11

At t s a es-ti .ot.j h .ten u i hee s. in

t e a kw s 11 1 9 orte-Ste...ansitlieethe tit nium sheet was matchedwithand ';sandw i ched between two'basic steel sheets and reheated to 1350F., and given three passesgon the Z high hot mill, finishing, thetitaniurn sheet at 18". x

. 4 The s e v th a'qk weresen rat kr u ng o t t n um's eet andtw basicfsheets.

. mpl 1 -3 The third 40'# ingot sheet at was similarly heated inacontinuous bar heating furnace under a reducing atmosphere toa 1520;F'.-:metal temperature and given four passeson-a-3-high hot mill to anelongation of 22",witha'225-feet-perminute finishing speed.'I'hepiece-wasjthenreheated to 1550 F. and given twoiipasses to anelongation of 40". The piece was: then taken to a continuous packheating'furnacewhere it was heated under a reducing atmosphere toapproximately 1350 F. metal temperaturezand given three single-plypasses on ax2-highyhot mill to an elongation of 80" and-a thickness of.'1-19, finishing at about 225 feet per'minute. Thesheet was sheared inhalf, matched in apairyandthe pair reheated to 1350 F.-in the continuouspack furnace and then given three passes on-the Z-high hot mill to 62" x.053.

At this stage; one ofthe" titanium sheets in the pack was sandwichedbetween twobasic steel sheets and reheated to 1350--F. and given-onepass on the 2-high hot mill and then hot-doubled, reheated, given twopasses on the -2-highl1ot mill to .033" gauge, reheated to: 1350'-F.-,-and given two further passes on the Z-high hotmill to 71 X .020". Thesheets in this pack were separated, producing two 71" x .020" titaniumsheets and-four basic steel sheets. v

The other titanium sheet from the 624' x-.053" pair was similarlysandwiched between two basic steel sheets and reheated to 1350 F. andgiven two passes onthe 2-high'hot.-mill, then hotdoubled, reheated to1350 and 'finishedr-with four passes on the 2-high hot millto 81 x.020", producing in the doubled" pack1tw0-81 x .020" titanium sheets andfour basicfsteel sheets.

Example I IJQ-A One of the 100# ingot sheet bars was similarly heated ina continuous bar heating furnace; under a reducing atmosphere to a l680F. smetal temperature and given four passes on-a-3- high hot mill to a22" elongation; with a 225-feet-perminute finishing speed. The piece wasthen reheated to 1480 F. and given four- :passes-on the 3-highmill-tc-van GIOIIgBItiQIIFOfAG: The-piece;

was then taken to a continuous pack heatin assua e 6 I- furnace where itwas heated under a reducing atmosphere to approximately 1480 F. andgiven I three single-ply passes on a- Z-highhotmill to an elongation of70" and a thickness of .118".

The sheet was sheared in half, matched in a pair,- and the pair reheatedto 1550 F. in a continuous pack furnace, and then given four passes onthe 2-high hot mill to 62 x .070". These titanium sheets at this stagewere so brittle with 10 no ductility thatno attempt was made to rollthem further. 7 r t 'It was impossible at this time to determineaccurately whether the higher heating temperaturesor the higher carbon,-iron,-and nitrogen in the original induction melted ingot wereresponsible'for these brittleness and lack of ductility characteristics;1 v

v I Example 100-3 The second 100# ingotsheet bar was similarly heated ina continuous bar heating furnace under a reducing atmosphereto a 1550 F.metal.temperature'and given six'ppasseson a 3-high hot mill to anelongation of 32 with a 225-feet-perminute finishing speed. The piecewas then reheated to 1500 F. and given four more passes 1 on the3-highmill toan elongationof 57''. The piece was then takento acontinuous pack heat- I ing' furnace where-it was heated under areducing atmosphere to approximately 13505 1 metal temperature and giventhree single-ply passes on a 2-high hot mill to an elongation of 751'.and a --thickness of .134. The sheetwas sheared in -"half, matchedin-arpair, and the pair reheated to l350 F. in the continuous'packfurnace and then -given five passes on-the 2-high mill to .7 m 1361" v H.Hereagain, the titanium sheets were so brittle and lackin in ductilitythat no further rolling 40 was performed. Since these titanium sheetsoriginated-from the-same ingot as the titanium sheets produced inExample 100-A, but 7 were heated and rolledwith temperatures and passescomparable to and on'the same equipment as the sheets rolled in Examples40-1, 40-2,-and 40-3,

. it 'is believed, that the higher carbon'content in the 100# ingot wasresponsible for the brittle- .ness andlack. of ductility. 7

All of the sheetsroller from the 4c# arc-melted ingots having low carboncontents, were ductile @and could be welded;--

Although very little scale. or oxide was formed on the titanium sheetsrolled-in the sandwiched packs, yetthe slight amount ofscale that did.form was very hard and tight but could be removed following heattreatment, including heati sing-to 1300 F. and-air cooling, byde-scaling in a-molten-sodium hydride bath followed by a nitrichydrofluoric acid-brightening dip, and finishing with a flattening passon-a Z-high cold mill.

The titanium sheetsrolled in the sandwiched packs tested 104 RockwellB-Scale hardness,

' while the basic steel sheets in said packs tested :.65-75 RockwellB-Scale hardness. V

In forging the titanium ingots .to formsheet bar, the metal was heatedto between 1700 F.

. and 1800- F. causing scaling which was removed .from the forged piecesby the surface conditioning operations. However, the ability to heat thesheet bar to froml520" F. to 1580.F., as in EX- amples 40-1, 40-2, and40-3, and toas high as 1680 F. inExample 100-A, without damagingthe-material, -,was a totally unexpected, result since those skilledinthe art indicate that 1300 ,-ra sinsecliptic umshtit nium can Safely;'b .heais rrol in s. ndi ated in hes mplc t higher heating took placein the continuous bar furnace for lieating the sheet bar, and a somewhatlower metal temperature of about 1350" F. (also above the indicated safe1300 F. temperature) was used in heating in the continuous pack furnace,

excepting in Example IOU-A where temperatures of 1480 'F. to l550 F.were used. However, these temperatures did not damage the material sincethe brittleness occurring in Example IOU-A was because of the highcarbon content of the titaniumrathrthan the high heating temperature. Webelievethat;itis'possible to heat titanium tothe temperature ranges setforth in the examples for hot rolling without damaging the materialprimarily because of the rapidity with which the material can be heatedin continuous furnaces and of therapidity. with which the material wasrolled on the 3-high and 2-high mills,

finishing atspeeds of 225Ifeet per minute. Since a reducing atmospherewas maintained in the continuous furnaceslittle or, no scaling occurredtherein, and the rapid rolling accomplished the necessary reductions toobtain the thin gauge' finished sheets of the order of .020" to .013" inthickness before any-damage to the material could occur as aresultof-the initially high temperaturesto which the material was heated forrolling.

We believe further-that it would be impossible to reduce'the material tosuch thin sheet gauges using the' high rolling temperatures, withoutfinishing at metal temperatures of the order of 1 100 F, to 1150 F., andwithout sandwichingindividual or multiple titanium sheets between basicsteel sheets not only to protect the titanium sheet surfaces inthe finalrolling operations, but also to retain high heating temperatures duringrolling.

Thus, theultimate essence of the present invention lies in the fact thatsheets of a metal dissimilar to titanium, such as basic steel sheets,

, are used to form a sandwich pack with the dissimilar metal sheets onthe outside of the pack in completing the rolling of titanium sheets toform large size, thin gauge titanium sheets. These sandwich packs of thetwo dissimilar metal sheets may be repeatedly heated and rolled todesired gauge with the optimum number of passes as in Examples 40-1 and40-3, or may be repeatedly heated and rolled accompanied by doublingasin Examples 40-1 and 40-3, or may be heated and rolled withoutdoubling as in Example 40-2. Furthermore, one titanium sheet may besandwiched between two sheets of a dissimilar metal as in Examples 40-2and 40-3, or a plurality of titanium sheets may be sandwiched I betweena plurality of sheets of a dissimilar metal ing; provides a procedure bywhich pure titanium .a. 91 i9na caexistinseprpb ems an stfic lencounteredin satisfying theneed for large size,

light gauge, ductile-hot rolled, titanium sheets in a simple,-economical and effective manner.

The hot; rolled titanium sheets .made in the manner described may,afterannealing and pickling be cold rolled to lighter gauges in a usualmanner to as much as 50% reduction when it-is desired to obtain coldrolled titanium sheet material, or when it, is desired to obtaintitanium sheet material thinner than hot rolled titanium 1 sheetmaterial which may be made in accordance with the presentinventi-on.

In the foregoing description, certain terms have been used for-brevity,clearness and understanding; but no -unnecessary limitations areto beimplied therefrom-beyond the requirements of the prior art, because suchterms are utilized for descriptive purposes hereinand not for thepurpose of limitation and ,are intended to be broadly construed.

- Moreover, the description of the improvements is by way of example,and the scope of the present invention isnot limited .tothe exactdetailsdescribed nor to the specific examples set forth.

Having now described the features, discoveries and principles of theinvention, the methods and procedures comprehended, the characteristicsof theproducts produced thereby, and the advantageous, new and usefulresults obtained; the new and useful discoveries, methods, steps,operations, procedures and principles, and mechanical equivalentsobvious to those skilled in the art, are set forth in the appendedclaims.

- We claim:

1. The methodof hot rolling thin gauge titanium sheets including thesteps of heating and rollingintermediate gauge titanium sheets fromsheet bar, sandwiching at least one intermediate gauge titanium sheetbetween two sheets of a dissimilar metal having 'a lower heatconductivity than titanium to form a sandwich pack, heating 7 androlling the pack to desired final titanium F. and rolling the pack todesired final titanium sheet gauge and protecting the titanium sheetmaterial from rapid heat loss and excessive oxidation by the dissimilarmetal sheets during heating and rolling of the sandwich pack to finaltitanium sheetgauge.

3. The method of hot rolling thin gauge titanium sheets including thesteps of rapidly heating titanium sheet bar to 1480 F. to 1680 F. andrapidly-rolling the same by a plurality of passes to elongate and thinthe metal, rapidly reheating the material to about 1350 F., andiurtherrapidly rolling the same bysingle-ply passes to intermediategauge; matching and rapidly heating and rolling the intermediate Igauge-material to further reduce the same; sandwiching at least onefurther reduced titanium sheet between two sheets of a dissimilar metalhaving lower heat conductivity than titanium to form a sandwich pack;rapidly heating and rolling the pack to desired final titanium sheetgauge, and protecting the titanium sheet material from rapid heat lossand excessive oxidation by the dissimilar metal sheets during heatingand rolling of the sandwich pack to final titanium sheet gauge.

4. The method of hot rolling thin gauge titanium sheets including thesteps of rapidly heating titanium sheet bar to 1480 F. to 1680 F. andrapidly rolling the same by a plurality of passes to elongate and thinthe metal, rapidly heating the material to about 1350 F. and furtherrapidly rolling the same by single-ply passes to intermediate gauge,matching and rapidly heating and rolling the intermediate gau ma erial tf r h r reduce the same, sandwiching at least one further reducedtitanium sheet between two basic steel sheets having a lower heatconductivity than titanium to form a sandwich pack, repeatedly heatingthe pack to 1350 F. and rolling the same accompanied by hot doubling todesired titanium sheet gauge, and protecting the titanium sheet materialfrom rapid heat loss and excessive oxidation by the steel sheets duringheating and rolling of the sandwich pack to final titanium sheet auge.

5. The method of hot rolling thin gauge titanium sheets including thesteps of rapidly heating titanium sheet bar to 1480 F. to 1680" F. andrapidly rolling the same by a plurality of passes to elongate and thinthe metal, rapidly heating the material to about 1350 F. and furtherrapidly rolling the same by single-ply passes to intermediate gauge,matching and rapidly heating and rolling the intermediate gauge materialto further reduce the same, sandwiching a further reduced titanium sheetbetween two basic steel sheets having a lower heat conductivity thantitanium to form a sandwich pack, reducing the pack to desired titaniumsheet gauge by operations of heating to 1350 F. and rolling, andprotecting the titanium sheet material from rapid heat loss andexcessive oxidation by the steel sheets during heating and rolling ofthe sandwich pack to final titanium sheet gauge.

6. The method set forth in claim 3 in which the matched intermediategauge titanium material prior to sandwiching is heated to 1350 F.,hot-doubled, reheated to 1350 F., rolled in doubled condition andsheared to remove the doubled end; and in which the four intermediategauge titanium sheets thus produced are sandwiched between two basicsteel sheets to form the sandwich pack.

'7. The method set forth in claim 4 in which the matched intermediategauge titanium material prior to sandwiching is heated to 1350 F.,hot-doubled, reheated to 1350 F., rolled in doubled condition andsheared to remove the doubled end; in which the four intermediate augetitanium sheets thus produced are sandwiched between the two basic steelsheets to form the sandwich pack; and in which the sandwich pack isheated to 1350 F., rolled by a plurality of passes, heated to 1350 F.and hot-doubled, reheated to 1350 F. and rolled by a plurality of passesto desired titanium sheet gauge.

8. The method set forth in claim 4 in which one intermediate gaugetitanium sheet is sandwiched between two basic steel sheets to form thesandwich pack; and in which the sandwich pack by a plurality of 1 isheated to 1350 F., rolled, heated to 1350 F. and hot-doubled, reheatedto 1350 F. and rolled by a plurality of passes to desired titanium sheetgauge.

9. The method set forth in claim 5 in which the sandwich pack of onetitanium sheet and two basic steel sheets is heated to 1350 F. androlled passes to desired final titanium sheet gauge.

10. The method of making hot rolled thin gauge titanium sheets from atitanium ingot including the steps of conditioning the ingot surfaces,repeatedly heatin the ingot to 1700 F. to 1850 F. and forming the sameto sheet bar size, conditioning the surfaces of the bar, repeatedlyheating and rolling the sheet bar to intermediate gauge titanium sheets,sandwiching at least one intermediate gauge titanium sheet between twobasic steel sheets having a lower heat conductivity than titanium toform a sandwich pack, heating and rolling the pack to desired finaltitanium sheet gauge, and protecting the titanium sheet material fromrapid heat loss and excessive oxidation by the steel sheets duringheating and rolling of the sandwich pack to final titanium sheet gauge.

11. The method as set forth in claim 10 in which the sheet bar israpidly heated to 1480 F. to 1680 F. and rapidly rolled by a pluralityof passes to elongate and thin the same, then reheated to about 1350 F.and further rapidly rolled by single-ply passes to intermediate gauge,and then matched and rapidly heated and rolled; and in which thesandwich pack is rapidly heated to 1350 F. and rolled to desired finaltitanium sheet gauge.

12. The method of making hot rolled thin gauge titanium sheets from atitanium ingot including the steps of conditioning the ingot surfaces,repeatedly heating the ingot to 1700 F. to 1850 F. and working the sameunder pressure to form sheet bar, conditioning the surfaces of the sheetbar, repeatedly heating and rolling the sheet bar to intermediate gaugetitanium sheets, sandwiching at least one intermediate gauge titaniumsheet between two sheets of a dissimilar metal having a lower heatconductivity than titanium to form a sandwich pack, heating the pack to1350 F. and rolling the same to desired titanium sheet gauge, andprotecting the titanium sheet material from rapid heat loss andexcessive oxidation by the dissimilar metal sheets during heating androlling of the sandwich pack to final titanium sheet gauge.

JAMES A. ROEMER. BURT H. McKIBBEN. JOSEPH R. CORRY.

References Cited in the file of this patent UNITED STATES PATENTS NameDate Parrock June 21, 1930 OTHER REFERENCES Number

1. THE METHOD OF HOT ROLLING THIN GAUGE TITANIUM SHEETS INCLUDING THE STEPS OF HEATING AND ROLLING INTERMEDIATE GAUGE TITANIUM SHEETS FROM SHEET BAR, SANDWICHING AT LEAST ONE INTERMEDIATE GUAGE TITANIUM SHEET BETWEEN TWO SHEETS OF A DISSIMILAR METAL HAVING A LOWER HEAT ONE INTERMEDIATE THAN TITANIUM TO FORM A SANDWICH PACK, HEATING AND ROLLING THE PACK TO DESIRED FINAL TITANIUM SHEET GAUGE, AND PROTECTING THE TITANIUM SHEET MATERIAL FROM RAPID HEAT LOSS AND EXCESSIVE OXIDATION BY THE DISSIMILAR METAL SHEETS DURING HEATING AND ROLLING OF THE SANDWICH PACK TO FINAL TITANIUM SHEET GAUGE. 